Compact Model of Impact Ionization in LDMOS Transistors

This paper presents a compact model of impact ionization currents in lateral double-diffused MOS (LDMOS) transistors. Depending on bias conditions, impact ionization in LDMOS transistors primarily occurs either in the intrinsic MOSFET or in the drift region, leading to a “double-hump” substrate current behavior and enhanced drain current when both V_G and V_D are high. Impact ionization in the drift region also causes the “expansion” effect, which is modeled by making the drift region resistance a function of the impact ionization current in the same region. The new model is verified by comparison with TCAD simulations and experimental data. The interaction between the expansion effect and self-heating is also accurately captured by the model.